Posts tagged caffeine consumption
Articles and news from the latest research reports.
Caffeine Consumption Within Six Hours Of Bedtime May Disrupt Sleep
Consumption of caffeine, even six hours before bedtime, can have significant, disruptive effects on sleep. The study, from the American Academy of Sleep Medicine, was published in the Journal of Clinical Sleep Medicine.
“Sleep specialists have always suspected that caffeine can disrupt sleep long after it is consumed,” said American Academy of Sleep Medicine President M. Safwan Badr, MD. “This study provides objective evidence supporting the general recommendation that avoiding caffeine in the late afternoon and at night is beneficial for sleep.”
The researchers found that 400 mg of caffeine (about 2-3 cups of coffee) taken at bedtime, or three to six hours before bedtime, significantly impacts sleep. Objectively measured total sleep time was reduced by more than an hour even when the caffeine was consumed six hours before going to bed. Subjective reports, however, suggest that the study participants were unaware of this sleep disturbance.
“Drinking a big cup of coffee on the way home from work can lead to negative effects on sleep just as if someone were to consume caffeine closer to bedtime,” said Christopher Drake, PhD, investigator at the Henry Ford Sleep Disorders and Research Center and associate professor of psychiatry and behavioral neurosciences at Wayne State University.
People tend to be less likely to detect the disruptive effects of caffeine on sleep when taken in the afternoon,” noted Drake, who is also on the board of directors of the Sleep Research Society.
The researchers recruited 12 healthy normal sleepers, as determined by a physical examination and clinical interview. Subjects were instructed to maintain their normal sleep schedule, but were given three pills a day for four days to be taken at six, three and zero hours before scheduled bedtime. Two of the pills were placebos, and one was 400 mg of caffeine. On one of the four days, all three of the participants’ pills were a placebo. The researchers measured sleep disturbance subjectively using a standard sleep diary and objectively using an in-home sleep monitor.
This is the first study to investigate the effects of a given dose of caffeine taken at different times before sleep. The findings suggest that, in order to allow healthy sleep, individuals should avoid caffeine after 5pm.
Caffeine consumption slows down brain development
Humans and other mammals show particularly intensive sleeping patterns during puberty. The brain also matures fastest in this period. But when pubescent rats are administered caffeine, the maturing processes in their brains are delayed. This is the result of a study supported by the Swiss National Science Foundation (SNSF).
Children’s and young adults’ average caffeine consumption has increased by more than 70 per cent over the past 30 years, and an end to this rise is not in sight: the drinks industry is posting its fastest-growing sales in the segment of caffeine-laden energy drinks. Not everybody is pleased about this development. Some people are worried about possible health risks caused in young consumers by the pick-me-up.
Researchers led by Reto Huber of the University Children’s Hospital Zurich are now adding new arguments to the debate. In their recently published study conducted on rats, the conclusions call for caution: in pubescent rodents, caffeine intake equating to three to four cups of coffee per day in humans results in reduced deep sleep and a delayed brain development.
Peak level during puberty
Both in humans and in rats, the duration and intensity of deep sleep as well as the number of synapses or connections in the brain increase during childhood, reaching their highest level during puberty and dropping again in adult age. “The brain of children is extremely plastic due to the many connections,” says Huber. When the brain then begins to mature during puberty, a large number of these connections are lost. “This optimisation presumably occurs during deep sleep. Key synapses extend, others are reduced; this makes the network more efficient and the brain more powerful,” says Huber.
Timid instead of curious
Huber’s group of researchers administered moderate quantities of caffeine to 30-day-old rats over five days and measured the electrical current generated by their brains. The deep sleep periods, which are characterised by slow waves, were reduced from day 31 until day 42, i.e. well beyond the end of administering caffeine. Compared to the rats being given pure drinking water, the researchers found far more neural connections in the brains of the caffeine-drinking animals at the end of the study. The slower maturing process in the brain also had an impact on behaviour: rats normally become more curious with age, but the rats consuming caffeine remained timid and cautious.
The brain goes through a delicate maturing phase in puberty, during which many mental diseases can break out. And even if the rat brain differs clearly from that of humans, the many parallels in how the brains develop raise the question as to whether children’s and young adults’ caffeine intake really is harmless or whether it might be wiser to abstain from consuming the pick-me-up. “There is still need for research in this area,” says Huber.
(Source: snf.ch)
Caffeine Improves Left Hemisphere Processing of Positive Words
A positivity advantage is known in emotional word recognition in that positive words are consistently processed faster and with fewer errors compared to emotionally neutral words. A similar advantage is not evident for negative words. Results of divided visual field studies, where stimuli are presented in either the left or right visual field and are initially processed by the contra-lateral brain hemisphere, point to a specificity of the language-dominant left hemisphere. The present study examined this effect by showing that the intake of caffeine further enhanced the recognition performance of positive, but not negative or neutral stimuli compared to a placebo control group. Because this effect was only present in the right visual field/left hemisphere condition, and based on the close link between caffeine intake and dopaminergic transmission, this result points to a dopaminergic explanation of the positivity advantage in emotional word recognition.